TWDM PON

[Amit Garg]

In one paper I have seen one architecture as given in attached file. for downstream transmission suppose 4 wavelengths are transmitting each at 10 GBPS. So total effective data rate is 40 GBPS. At remote node there is one 1X4 power splitter to provide service to 4 ONUs. Each output port of splitter will consists all four wavelength each at 2.5 GBPS (If I am right). Now Each ONU can receive (or tuned at single wavelength at a time) only one wavelength and that wavelength will only provide 2.5 GBPS.

Now I want to know that what is the need of 4 transmitters or Hybrid TWDM PON at OLT when in TDM PON, only one transmitter will be able to provide 2.5GBPS to all four ONUs ??

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[alistu]

Hi Amit,

Actually, bit rate of each of the channels does not change. If a channel is sending 10Gbps, then at the receiver side, each of the ONUs receive with a bit rate of 10Gbps. What splitter does is splitting the power (and not bit rate). Then each UNO receives their own wavelength and the total bit rate is 10Gbps x 4 = 40 Gbps.

Regards

[Amit Garg]

Dear Alistu
I agreed with you and I was also thinking like you. But I am in doubt that if power splitter is not splitting the bit rate than each ONU will receive the bit rate of 10 GBPS. In below attached file (table) how average bandwidth is divided to all users. I am little bit in confuse about the the relation between BIT RATE and BANDWIDTH. please explain it also.

thanks in advance.

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[alistu]

Sure! In WDM, Each channel produces their own iformation independent of the other channels. The higher the bit rate, the more the bandwidth nneded for each of these separate channels. Then the channels are multiplexed, with each of them having a carrier frequency (or wavelegth) different than the others (with a spacing so that they won’t overlap in frequency domain) to enter the line. The bandwidth for each channel is still the same as it was when the channels were formed separately and they still maintain their bit rate.

At the receiver, they are demultiplexed (which means their carrier frequency is omitted so that they become the same as they were before multiplexing), so their bandwidth and bit rate remain unchanged. And that’s it! Now if the bandwidth for each channel (including spacing) is, say, 50GHz, the overall bandwidth for the signal after multiplexing and before demultiplexing for a 4 user system is 4 x 50 = 200GHz. But when the signal is demultiplexed, each user again has a signal with bandwidth of 50 GHz. And the bit rate for each channel has not changed.

[Amit Garg]

Dear Alistu
Suppose we are using 4 transmitters (4 channels) each transmitting at bit rate of 10GBPS after multiplexing and passing through fiber cable and combined signal is passed through 1×4 power splitter as shown in attached file. Now each ONU is receiving 40 GBPS (all channels). My question is that how an ONU will access the 40GBPS while it is tuned on a single wavelength (10 GBPS)??

Attachments:

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   14.jpg
   

[alistu]

It is true that the power splitter only splits the power, but after the power splitter, there are filters tuned at the corresponding wavelengths of the users. This is shown in the image you have attached in your main post (each color corresponds to a certain wavelength). You can also have a look at your snapshot in which I have shown filters’ place and wavelengths. Please see if it clarifies the matter.

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   snap-WDM.jpg
   

[Amit Garg]

That means, each ONU is accessing only 10 GBPS than how average bandwidth per ONU is by using 4 transmitters??

[alistu]

Dear Amit,

I believe the table you have attached in your reply #25173 (which you are now referring to) belongs to the systems with Time Division Multiplexing, and not Wavelength Division Multiplexing as we have discussed here. You may see “TDM-PON Comparison” on the label of the table.

Regards

[Ashu verma]

Hi! Amit
Since Alistu is continuously answering and explained well about WDM PON.Eventhough you seems quite confused in the concept of TDM PON and WDM PON and basically the advantage of WDM-PON over TDM PON.Then i would suggest to go through the links given below
http://www.championone.com/uploads/documents/appnotes/The%20difference%20between%20a%20PASSIVE%20WDM%20network%20and%20PON.pdf
However for the detailed review of PON standards you can go to
https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&cad=rja&uact=8&ved=0CDgQFjADahUKEwiDqPTG6ZHIAhUSJI4KHQrjAU0&url=http%3A%2F%2Fwww.springer.com%2Fcda%2Fcontent%2Fdocument%2Fcda_downloaddocument%2F9781461439387-c1.pdf%3FSGWID%3D0-0-45-1372106-p174422538&usg=AFQjCNGF3iQN-KBV6EDtLukHpzvhdZ0RpQ&sig2=YHUdf8sLl30o43-uTvmQ5w
Thank you

[Ashu verma]

For making your doubt more specific and detailed manner,could you please provide the article you are working on or trying to reproduce?
It would be then easy to state and let you know in better way.In forum itself many time basic difference had been elaborated and discussed,kindly try to access them too.
Regards

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